Individual differences in the perception of dichotic chords.

A new method was employed to measure the changes in the strength of ear dominance in the perception of dichotic chords as a function of stimulus intensity. The results of the first experiment, where the right and left tones were of equal intensity, revealed striking individual differences in the way the ear dominance of five subjects changed as the intensity of the chords was varied over a 60-dB range--no two subjects exhibiting the same pattern of behavior. Since, within the context of the model of Yund and Efron [J. Acoust. Soc. Am. 62, 607-617 (1977)] these individual differences could result from right-left asymmetries in the subject's intensity-response (I-R) transduction mechanisms, a second experiment was performed in which the two tones had different intensities. From the results of the second experiment the shape of the I-R function for each ear could be computed. Using these I-R functions as parameters, the model accurately predicted the idiosyncratic changes of ear dominance observed in the first experiment. The right-left asymmetries in the I-R functions also a-count for previously reported idiosyneratic changes in ear dominance as a function of the frequency difference between the two tones of the dichotic chord.